The present invention relates to reciprocating piston engines and, in particular, to an engine of this nature in which a piston reciprocates in a cylinder within which zones having differences in fuel enrichment are established.
The cylinder, furthermore, comprises a head having means for establishing directionally oriented gas flow into the cylinder.
It is known to subdivide an engine cylinder to establish chambers to which fuels for different enrichment of the air are supplied. In such engines, the richer mixture is ignited and the mixture of lesser richness is ignited from the richer mixture. Engines of this nature are stable under various load conditions, including constant load, but have a high rate of fuel consumption and are characterized by high direct and indirect heat losses (to the walls and exhaust gases respectively).
It is also known to construct engines in which the cylinder space is not subdivided but which include devices for generating regions of differing fuel-air mixtures within the cylinder. Such engines have a better fuel economy than the ones referred to above when the motor is under less than full load and, like the first mentioned engine, have a low quantity of noxious emissions in the exhaust gases. This last mentioned type of engine is, however, unstable in operation. In order to utilize the thermodynamic advantages resulting from the combustion of lean mixtures, stratified-charge engines without secondary combustion chambers have ben designed which distribute the basic mixture over the entire available space. In such engines, air flows into the cylinder through valves disposed in an off-center position. The open inlet valve projecting into the compression space in an off-center position, the off-center gas inflow and partial shrouding of the valve gap produce a very strong gas turbulence in the cylinder. If fuel is then injected into the piston-swept or compression space at the start of the compression stroke, a fuel-air mixture distributed over the the entire space is produced in the cylinder as a result of the gas turbulence. It is true that certain zones of the air are enriched with fuel if fuel is injected just before ignition, but this is not a mixture formation which can be used for favorable combustion. The very slow flame propagation in very lean mixtures has considerable drawbacks with respect to thermal efficiency.
However, if the mixture is concentrated primarily in the inner region of the combustion space, then the resulting flame travels are very short so that even lean mixtures can be burned with sufficient speed. If a ring of air envelopes the burning gases, such a ring has an isolating effect so that thermodynamically and in terms of heat losses the system (air-enveloped mixture zone plus air-enveloped burning gases) behaves similar to a system in which the same amount of fuel is distributed over the entire available space and the entire air and in which the lean mixture is burned with sufficient speed.
If the intake air is not throttled, then a large amount of gas is contained in the comparatively small-volume air-enveloped mixture zone. In the upper load range, the amount of gas contained in the mixture zone is increased by pressure charging so that the power output is similar to that of a comparable Otto-cycle engine.
The object of the present invention is the construction of a reciprocating piston engine in such a manner that mixing zones are established in the cylinder which show different ratios of fuel to air thereby obtaining the advantages of the type of engine in which a richer fuel-air mixture is ignited which, in turn, ignites a lower ratio fuel-air mixture, thus improving thermal efficiency and reducing the emission of pollutants.
One object of the present invention is the provision of a reciprocating piston engine of the nature referred to which is stable in operation under all load conditions.
A further object of the present invention is the formation of at least one helical stream of fuel-air mixture which is then transformed to a zone of mixture enclosed by a ring and/or cylinder of pure air to increase thermal efficiency. A further object of the invention is the reduction in length of flame travel.